Rocky Shore1 Intertidal Communities Rocky Shore Communities

Rocky Shore2 The Intertidal The intertidal zone is the area between the highest high and the lowest low tide Organisms that live in this area undergo the greatest variations in environmental conditions

Rocky Shore3 Tidal Forces Gravitational pull on the earth by the sun and moon combined with centrifugal force generated by the earth-moon-system Semidiurnal tides Diurnal tides

Spring and Neap Tides

Rocky Shore5 Rocky Intertidal Community Rocky coasts usually occur on steep coasts that lack sediment Fort Fisher is one of the only naturally occurring rocky outcrops in the S.E. U.S. Epifauna Sessile

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7 Abiotic Factors Desiccation Extreme changes in temperature Changes in salinity Turbulence

Rocky Shore8 Water Loss For survival the duration of exposure to air is critical Sessile animals have structural adaptations

Rocky Shore9 Dessication Algae - can withstand % of water loss in tissues and survive Littorina sp. (Periwinkle) reduce area in contact with the substrate and have a light colored shell to deal with extreme heats Algae mat at low tide

Rocky Shore10 Changes in Temperature Due to its high heat capacity water shows a minimum change in temperature when compared with the air If extreme temperature does not kill an organism it may severely weaken it and cause it to die of secondary causes Extreme temperatures may hasten desiccation Adaptations

Rocky Shore11 Drastic Fluctuations in Salinity Salinity may change due to severe rainfall If severe enough at low tide the entire community may experience high mortality

Rocky Shore12 Wave Action Waves act to smash and tear organisms from the substrate Sessile animals use cement (barnacles), holdfasts (seaweeds) and, byssal threads (mussels) Mobile animals have appendages for clinging and snails have an enlarged foot used for attachment Wave action also effects the intertidal by disturbing the substrate

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Rocky Shore14 Modes of Feeding Due to the lack of sediment there are no deposit feeders! Almost all of the sessile animals are filter or suspension feeders Heavy wave action also effects feeding Suspension Feeding Barnacles

Rocky Shore15 Vertical Zonation Species settle in specific vertical bands based on their ability to withstand exposure to air The rocky intertidal provides many microhabitats (Numerous niches) High species diversity Distinct banding which progress from the low tide line to the high tide line Zonation occurs due to a both physical and biological interactions

Rocky Shore16 Rocky Shore Zonation Organisms are found in a given area by their ability to compete and deal with physical factors. Most animals in the intertidal live near the upper end of their lethal limits Lower distribution is determined by competition and predation

Supralittoral zone Midlittoral zone Infralittoral

Rocky Shore18 Biotic Factors Competition Due to the limited amount of area, competition for space is acute Succession – natural progression of communities The creation of open spaces results in quick colonization by opportunistic species. Soon replaced by slower growing competitively dominant spp.

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Keystone Predators Keystone species: a single species, which has a controlling effect on the community in which it lives

Rocky Shore21 Tide pools Animals have the same physical factors to contend with Closed Tide Pools Open Tide pools